The overall objectives of the project are two-fold: 1. To study the mechanism of the initial interaction of cytokinin and cytoplasmic receptor molecules. 2. To compare the nature of the cytokinin-binding proteins from the "normal" (cytokinin-heterotrophic) and the "autonomous" (cytokinin-autotrophic, a mutant of the "normal" strain) tobacco pith culture cells. The knowledge obtained from these model system studies will aid in understanding cell division and differentiation in other organisms.